The use of data processing systems comprising processing elements and memory elements have become widespread in very different fields of electronics. In the field of communication, most communication devices contain processors that execute programs stored in appropriate memory devices, to thereby process data stored in the same memory devices or somewhere else. A typical example of a communication device containing a processor (typically a microprocessor controller) and appropriate memory chips is a mobile telephone.
One of the problems encountered with data processing systems is that of data security. For example, the above-mentioned mobile phone may contain different types of memories separated from the central processor, such as a flash memory or an EEPROM. It is possible that an EEPROM is emulated by a flash memory or is partly a flash memory. Such memories typically have to be protected against unauthorized access, in order to safeguard the normal operation of the mobile telephone.
Naturally, the problem of data security occurs in any such data processing system, not only in mobile phones. The basic solution to problems of data security is the provision of protection software, e.g. an algorithm for the authentication of sensitive data in the EEPROM or emulated EEPROM. However, such software solutions suffer from a number of problems that cannot be overcome by software itself, such as the possibility of switching off the authentication algorithm or modifying the authentication algorithm. Sometimes, it is also possible to circumvent an authentication algorithm by using older software that did not contain the authentication routine but still provides access to the sensitive data.